Characterization of Viruses in Phase 3 and Phase 3b Trials (the Ring Study and the Dapivirine Ring Extended Access and Monitoring Trial) of the Dapivirine Vaginal Ring for Human Immunodeficiency Virus Type 1 Infection Risk Reduction.

BACKGROUND: The Ring Study demonstrated 35.1% human immunodeficiency virus type 1 (HIV-1) infection risk reduction among participants who used the Dapivirine vaginal ring-004 (DVR), whereas the Dapivirine Ring Extended Access and Monitoring (DREAM) trial, approximated a 62% risk reduction. The observed non-nucleoside reverse-transcriptase inhibitor (NNRTI) resistance-associated mutations (RAMs) and effects on viral susceptibility are described here. METHODS: Population-based genotyping on plasma samples collected longitudinally, and next-generation sequencing (NGS) and phenotypic susceptibility testing were done on plasma collected at seroconversion. Retrospective HIV-1 RNA testing was used to more accurately establish the time of infection. RESULTS: In the Ring Study, NNRTI RAMs were not observed in most viruses at seroconversion (population-based genotyping: DVR: 71 of 84, 84.5%; placebo: 50 of 58, 86.2%). However, more E138A was found in the DVR group (E138A DVR: 9 of 84, 10.7%; placebo: 2 of 58, 3.4%; P = .2, Fisher exact test). NGS detected 1 additional mutation in each group (DVR: G190A; placebo: G190A and G190E). Marginal dapivirine susceptibility reduction was found with NNRTI RAMs at seroconversion (geometric mean fold-change, range: DVR, 3.1, 1.3-5.1; placebo, 5.8, 0.9-120). NNRTI RAMs were not emergent between first detectable HIV-1 RNA and seroconversion when these visits differed (paired samples, mean ring use: DVR, n = 52, 35 days; placebo, n = 26, 31 days). After stopping DVR, 2 of 63 viruses had emergent G190G/A or K103K/N with V106V/M at final study visit. Resistance profiles from the DREAM trial were consistent with the Ring Study. CONCLUSIONS: DVR showed little potential for selection of NNRTI-resistant variants. CLINICAL TRIALS REGISTRATION: NCT01539226 and NCT02862171.

Clinical Presentation, Treatment Response, and Virology Outcomes of Women Who Seroconverted in the Dapivirine Vaginal Ring Trials-The Ring Study and DREAM.

BACKGROUND: Participants with human immunodeficiency virus (HIV) seroconversion in The Ring Study, a phase 3 trial of dapivirine vaginal ring (DVR), or in the open-label extension trial dapivirine ring extended access and monitoring (DREAM) were offered enrollment in an observational cohort study (IPM 007) to assess clinical presentation and response to antiretroviral therapy (ART). METHODS: Participants' HIV infection was managed at local treatment clinics according to national treatment guidelines. IPM 007 study visits occurred 3 and 6 months after enrollment and every 6 months thereafter. Assessments included plasma HIV-1 RNA, CD4+ T-cell counts, and recording of HIV/AIDS-associated events and antiretroviral use. Post hoc virology analyses were performed for participants identified with virologic failure. RESULTS: One hundred fifty-one of 179 eligible participants (84.4%) enrolled into IPM 007; 103 had previously received the DVR in the Ring or DREAM studies, and 48 had received placebo in The Ring Study. HIV-1 RNA and CD4+ T-cell counts after 12 months' follow-up were similar for participants who used the DVR in The Ring Study and DREAM, compared to those who received placebo. Of the 78 participants with a study visit approximately 6 months after ART initiation, 59 (75.6%) had HIV-1 RNA <40 copies/mL (The Ring Study: placebo: 13/23 [56.5%]; DVR: 32/39 [82.1%]; DREAM [DVR]: 14/16 [87.5%]). Post hoc virology analysis indicated that genotypic patterns observed at virologic failure were as expected of a nonnucleoside reverse transcriptase inhibitor (NNRTI)-based regimen. CONCLUSIONS: Seroconversion during DVR use did not negatively affect clinical presentation or treatment outcome. Mutation patterns at virologic failure were in line with individuals failing an NNRTI-based regimen. CLINICAL TRIALS REGISTRATION: NCT01618058.

Safety, adherence, and HIV-1 seroconversion among women using the dapivirine vaginal ring (DREAM): an open-label, extension study.

BACKGROUND: The Ring Study, a phase 3 trial in 1959 sexually active women (randomised 2:1), showed a favourable safety profile and a 31% HIV-1 infection risk reduction for a vaginal ring containing 25 mg of dapivirine, compared with a placebo ring. We report here the DREAM study, which aimed to evaluate safety, adherence, and HIV-1 incidence in those using the dapivirine vaginal ring (DVR) in open-label use. METHODS: The DREAM study is an open-label extension of The Ring Study, done at five research centres in South Africa and one research centre in Uganda. Former participants from The Ring Study, who remained HIV-negative and who did not discontinue the study due to an adverse event or safety concern that was considered to be related to the investigational product, were eligible. Women who were pregnant, planning to become pregnant, or breastfeeding at screening for DREAM were excluded. All participants received the DVR for insertion at the enrolment visit. Participants attended a 1-month follow-up visit and could either proceed with visits once every 3 months or attend monthly visits up to month 3 and then continue with visits once every 3 months. At each visit, HIV testing and safety evaluations were done, and residual dapivirine measured in used rings (approximately 4 mg is released from the DVR over 28 days of consistent use). HIV-1 incidence was compared descriptively with the simulated incidence rate obtained from bootstrap sampling of participants in the placebo group of The Ring Study, matched for research centre, age, and presence of sexually transmitted infections at enrolment. This study is registered with ClinicalTrials.gov, NCT02862171. FINDINGS: Between July 12, 2016, and Jan 11, 2019, 1034 former participants from The Ring Study were screened, 941 were enrolled and 848 completed the trial. 616 (65·5%) of 941 participants reported treatment-emergent adverse events. Of these, six (0·6%) had events considered to be treatment-related. No treatment-related serious adverse events were reported. Measurements of monthly ring residual amounts in participants enrolled in both trials showed consistently lower mean values in DREAM than in The Ring Study. Arithmetic mean ring residual amounts of participants in The Ring Study DVR group who enrolled in DREAM were 0·25 mg lower (95% CI 0·03-0·47; p=0·027) than the mean ring residual amounts of these participants in The Ring Study. 18 (1·9%) HIV-1 infections were confirmed during DVR use, resulting in an incidence of 1·8 (95% CI 1·1-2·6) per 100 person-years, 62% lower than the simulated placebo rate. INTERPRETATION: Although efficacy estimation is limited by the absence of a placebo group, the observed low HIV-1 incidence and improved adherence observed in DREAM support the hypothesis that increased efficacy due to improved adherence occurs when women know the demonstrated safety and efficacy of the DVR. The feasibility of a visit schedule of once every 3 months was shown, indicating that the DVR can be used in a real-world situation in usual clinical practice. FUNDING: The Ministry of Foreign Affairs (MFA) Denmark, Flanders MFA, Irish Aid, Dutch MFA, UK Aid from the UK Government's Foreign, Commonwealth and Development Office, and the US President's Emergency Plan for AIDS Relief through the US Agency for International Development.

First prospective comparison of genotypic versus phenotypic tropism assays in predicting virologic responses to maraviroc in a phase 3 study.

Maraviroc (MVC, a CCR5 antagonist) is only fully active against CCR5 tropic [R5] HIV-1, and tropism testing is required prior to initiating treatment. The MODERN study prospectively compared genotypic (GTT) and phenotypic (Trofile®) tropism testing with treatment-naive HIV-1-infected participants randomized 1:1 to either GTT or Trofile tropism assessments. Participants with R5 virus were randomized 1:1 to receive darunavir/ritonavir (DRV/r) with either MVC or tenofovir/emtricitabine. Screening samples were also retrospectively tested using the alternative assay. Positive predictive values (PPVs) for each assay were estimated using both the observed MVC+DRV/r response rate (HIV-1 RNA <50 copies/mL at Week 48) and model-based response estimates. The observed MVC+DRV/r response rate was 146/181 (80.7%) for GTT versus 160/215 (74.4%) for Trofile, with a stratification adjusted difference of 6.6% (95% CI, -1.5% to 14.7%) in favor of GTT. The model-based PPV estimates (±standard error) were 80.5% (±2.38) and 78.0% (±2.35) for GTT and Trofile, respectively (difference, 2.5%; 95% CI, -2.0% to 7.0%). Most participants had R5 results using both assays (285/396; 72%) and, of those, 79.3% (226/285) had HIV-1 RNA <50 copies/mL at Week 48. Both the genotypic and phenotypic tropism assays evaluated can effectively predict treatment response to MVC.

Clonal analysis of HIV-1 genotype and function associated with virologic failure in treatment-experienced persons receiving maraviroc: Results from the MOTIVATE phase 3 randomized, placebo-controlled trials.

Detailed clonal phenotypic/genotypic analyses explored viral-escape mechanisms during maraviroc-based therapy in highly treatment-experienced participants from the MOTIVATE trials. To allow real-time assessment of samples while maintaining a blind trial, the first 267 enrolled participants were selected for evaluation. At failure, plasma samples from 20/50 participants (16/20 maraviroc-treated) with CXCR4-using virus and all 38 (13 maraviroc-treated) with CCR5-tropic virus were evaluated. Of those maraviroc-treated participants with CXCR4-using virus at failure, genotypic and phenotypic clonal tropism determinations showed >90% correspondence in 14/16 at Day 1 and 14/16 at failure. Phylogenetic analysis of clonal sequences detected pre-treatment progenitor CXCR4-using virus, or on-treatment virus highly divergent from the Day 1 R5 virus, excluding possible co-receptor switch through maraviroc-mediated evolution. Re-analysis of pre-treatment samples using the enhanced-sensitivity Trofile® assay detected CXCR4-using virus pre-treatment in 16/20 participants failing with CXCR4-using virus. Post-maraviroc reversion of CXCR4-use to CCR5-tropic occurred in 7/8 participants with follow-up, suggesting selective maraviroc inhibition of CCR5-tropic variants in a mixed-tropic viral population, not emergence of de novo mutations in CCR5-tropic virus, as the main virologic escape mechanism. Maraviroc-resistant CCR5-tropic virus was observed in plasma from 5 treated participants with virus displaying reduced maximal percent inhibition (MPI) but no evidence of IC50 change. Env clones with reduced MPI showed 1-5 amino acid changes specific to each V3-loop region of env relative to Day 1. However, transferring on-treatment resistance-associated changes using site-directed mutagenesis did not always establish resistance in Day 1 virus, and key 'signature' mutation patterns associated with reduced susceptibility to maraviroc were not identified. Evolutionary divergence of the CXCR4-using viruses is confirmed, emphasizing natural selection not influenced directly by maraviroc; maraviroc simply unmasks pre-existing lineages by inhibiting the R5 virus. For R5-viral failure, resistance development through drug selection pressure was uncommon and manifested through reduced MPI and with virus strain-specific mutational patterns.

Pharmacokinetics, safety and efficacy of maraviroc in treatment-experienced pediatric patients Infected with CCR5-tropic HIV-1

BACKGROUND: Maraviroc is a CC-chemokine receptor 5 antagonist approved to treat adults infected with CC-chemokine receptor 5-tropic (R5) HIV-1. Study A4001031 was conducted to evaluate the pharmacokinetics, safety and efficacy of maraviroc in combination with optimized background therapy in treatment-experienced pediatric patients infected with R5 HIV-1 and support registration of maraviroc for pediatric use. METHODS: This is an open-label, 2-stage, age-stratified, noncomparative multicenter study. One-hundred and three participants were enrolled into 4 age/formulation cohorts and dosed twice daily. Initial doses were determined by body surface area and optimized background therapy, based on drug interactions with maraviroc in adults. Dose adjustment and pharmacokinetic reevaluation occurred if the average concentrations (Cavg) at Week 2 were <100 ng/mL (Stage 1-dose finding). RESULTS: Data from the Week 48 analysis demonstrated that 49/50 Stage 1 participants rolling over into Stage 2 (safety and efficacy) achieved Cavg ≥100 ng/mL. Doses were identified that achieved similar concentration ranges to those seen in adults. The majority (90/103) received optimized background therapy containing potent cytochrome P450 3A inhibitors. Maraviroc was well tolerated and the safety and efficacy were comparable to those of adults. All cohorts had a mean decrease from baseline in HIV-1 RNA of >1 log10. Increases from baseline in the median CD4+ cell count and percentage were seen for all age groups. CONCLUSIONS: The maraviroc dosing strategy resulted in participants achieving the target Cavg, with exposure ranges similar to those observed in adults on approved doses. The safety and efficacy of maraviroc in this pediatric population were comparable to those seen in adults

Pharmacokinetics, Safety and Efficacy of Maraviroc in Treatment-experienced Pediatric Patients Infected With CCR5-Tropic HIV-1.

BACKGROUND: Maraviroc is a CC-chemokine receptor 5 antagonist approved to treat adults infected with CC-chemokine receptor 5-tropic (R5) HIV-1. Study A4001031 was conducted to evaluate the pharmacokinetics, safety and efficacy of maraviroc in combination with optimized background therapy in treatment-experienced pediatric patients infected with R5 HIV-1 and support registration of maraviroc for pediatric use. METHODS: This is an open-label, 2-stage, age-stratified, noncomparative multicenter study. One-hundred and three participants were enrolled into 4 age/formulation cohorts and dosed twice daily. Initial doses were determined by body surface area and optimized background therapy, based on drug interactions with maraviroc in adults. Dose adjustment and pharmacokinetic reevaluation occurred if the average concentrations (Cavg) at Week 2 were <100 ng/mL (Stage 1-dose finding). RESULTS: Data from the Week 48 analysis demonstrated that 49/50 Stage 1 participants rolling over into Stage 2 (safety and efficacy) achieved Cavg ≥100 ng/mL. Doses were identified that achieved similar concentration ranges to those seen in adults. The majority (90/103) received optimized background therapy containing potent cytochrome P450 3A inhibitors. Maraviroc was well tolerated and the safety and efficacy were comparable to those of adults. All cohorts had a mean decrease from baseline in HIV-1 RNA of >1 log10. Increases from baseline in the median CD4+ cell count and percentage were seen for all age groups. CONCLUSIONS: The maraviroc dosing strategy resulted in participants achieving the target Cavg, with exposure ranges similar to those observed in adults on approved doses. The safety and efficacy of maraviroc in this pediatric population were comparable to those seen in adults.

Development of maraviroc, a CCR5 antagonist for treatment of HIV, using a novel tropism assay.

Assays to identify infectious organisms are critical for diagnosis and enabling the development of therapeutic agents. The demonstration that individuals with a 32-bp deletion within the CCR5 locus were resistant to human immunodeficiency virus (HIV) infection, while those heterozygous for the mutation progressed more slowly, led to the discovery of maraviroc (MVC), a CCR5 antagonist. As MVC is only active against CCR5-tropic strains of HIV, it was critical to develop a diagnostic assay to identify appropriate patients. Trofile™, a novel phenotypic tropism assay, was used to identify patients with CCR5-tropic virus for the MVC development program. Results of these clinical studies demonstrated that the assay correctly identified patients likely to respond to MVC. Over time, the performance characteristics of the phenotypic assay were enhanced, necessitating retesting of study samples. Genotypic tropism tests that have the potential to allow for local use and more rapid turnaround times are also being developed.

The maraviroc expanded access program - safety and efficacy data from an open-label study.

PURPOSE: The maraviroc (MVC) expanded access program (EAP) was initiated to increase MVC availability to patients with limited treatment options. Darunavir (DRV), raltegravir (RAL), and etravirine (ETV) were either recently approved or under regulatory review at study initiation and available for coadministration with MVC. Thus, the safety of MVC in combination with new antiretroviral therapies (ARVs) could be assessed. This open-label safety study of MVC was conducted at 262 sites worldwide in 1032 R5 HIV-positive treatment-experienced patients with limited/no therapeutic options. METHODS: Study visits included screening, baseline, end of study or early discontinuation, and follow-up 30 days after last dose. Interim visits for HIV-1 RNA and CD4 cell counts occurred according to local HIV infection management guidelines. Safety data were analyzed overall and by subgroup based on ARV combination [MVC+optimized background therapy (OBT), MVC ± OBT+DRV/r, MVC ± OBT+RAL, MVC ± OBT+RAL+DRV/r, MVC ± OBT+RAL+ETV ± DRV/r]. RESULTS: Most (90.3%) adverse events (AEs) were of mild or moderate severity with few grade 3/4 events, discontinuations, or temporary discontinuations/dose reductions due to AEs or serious AEs. Similar results were observed across subgroups. Of treated patients, 79.9% and 50% had HIV-1 RNA < 400 copies/ml and < 50 copies/ml respectively, at the end of the study, early termination visits, or at last known status. Tropism changes and selection of MVC-resistant R5 virus, including high-level MVC dependence, were mechanisms of viral escape. CONCLUSION: MVC was well tolerated with virologic suppression observed in most patients.

Efficacy and safety of maraviroc vs. efavirenz in treatment-naive patients with HIV-1: 5-year findings.

OBJECTIVE: Maraviroc, a chemokine co-receptor type 5 (CCR5) antagonist, has demonstrated comparable efficacy and safety to efavirenz, each in combination with zidovudine/lamivudine, over 96 weeks in the Maraviroc vs. Efavirenz Regimens as Initial Therapy (MERIT) study. Here we report 5-year findings. DESIGN: A randomized, double-blind, multicenter phase IIb/III study with an open-label extension phase. METHODS: Treatment-naive patients with CCR5-tropic HIV-1 infection (Trofile) received maraviroc 300 mg twice daily or efavirenz 600 mg once daily, and zidovudine/lamivudine 300 mg/150 mg twice daily. After the last patient's week 96 visit, the study was unblinded and patients could enter a nominal 3-year open-label phase. Endpoints at the 5-year nominal visit (week 240) included proportion of patients (CCR5 tropism re-confirmed by enhanced sensitivity Trofile) with viral load (plasma HIV-1 RNA) below 50 and 400 copies/ml, and change from baseline in CD4(+) cell count, as well as safety. RESULTS: The proportion of patients maintaining viral load below 50 copies/ml was similar between treatment arms throughout the study and at week 240 (maraviroc 50.8% vs. efavirenz 45.9%). Maraviroc-treated patients had a greater increase from baseline in mean CD4(+) cell count than efavirenz-treated patients at week 240 (293 vs. 271 cells/µl, respectively). Fewer patients on maraviroc vs. efavirenz experienced treatment-related adverse events (68.9 vs. 81.7%) and discontinued as a result of any adverse event (10.6 vs. 21.3%). CONCLUSION: Maraviroc maintained similar long-term antiviral efficacy to efavirenz over 5 years in treatment-naive patients with CCR5-tropic HIV-1. Maraviroc was generally well tolerated with no unexpected safety findings or evidence of long-term safety concerns.

An exploratory survey measuring stigma and discrimination experienced by people living with HIV/AIDS in South Africa: the People Living with HIV Stigma Index.

BACKGROUND: The continued presence of stigma and its persistence even in areas where HIV prevalence is high makes it an extraordinarily important, yet difficult, issue to eradicate. The study aimed to assess current and emerging HIV/AIDS stigma and discrimination trends in South Africa as experienced by people living with HIV/AIDS (PLHIV). METHODS: The PLHIV Stigma Index, a questionnaire that measures and detects changing trends in relation to stigma and discrimination experienced by PLHIV, was used as the survey tool. The study was conducted in 10 clinics in four provinces supported by the Foundation for Professional Development (FPD), with an interview total of 486 PLHIV. A cross-sectional design was implemented in the study, and both descriptive and inferential analysis was conducted on the data. RESULTS: Findings suggest that PLHIV in this population experience significant levels of stigma and discrimination that negatively impact on their health, working and family life, as well as their access to health services. Internalised stigma was prominent, with many participants blaming themselves for their status. CONCLUSION: The findings can be used to develop and inform programmes and interventions to reduce stigma experienced by PLHIV. The current measures for dealing with stigma should be expanded to incorporate the issues related to health, education and discrimination experienced in the workplace, that were highlighted by the study.

Baseline CD4(+) T-cell counts and weighted background susceptibility scores strongly predict response to maraviroc regimens in treatment-experienced patients.

BACKGROUND: Maraviroc-containing regimens are known to achieve virological suppression in many treatment-experienced patients. This study aimed to evaluate a more rigorous methodological approach to resistance-response analysis in large clinical studies and to better establish which subpopulations of patients were most likely to benefit from maraviroc by refining and extending previous subgroup analyses from the MOTIVATE studies. METHODS: Individual weighted optimized background therapy (OBT) susceptibility scores were calculated by combining genotypic or phenotypic resistance testing with prior drug use information. Virological response (HIV-1 RNA<50 copies/ml at week 48) using each of these methods was compared with a commonly used method of counting active drugs. Baseline predictors of virological response, including weighted or unweighted scoring, maraviroc use, baseline CD4(+) T-cell count, HIV-1 plasma viral load and tropism, were assessed by logistic regression modelling. RESULTS: Genotypic or phenotypic weighted methods were similarly predictive of virological response and better than counting active drugs. Weighted scoring and baseline CD4(+) T-cell count were the strongest predictors of virological response (P<0.0001): ≈70% of maraviroc patients with a weighted score ≥2 had a virological response, rising to ≈80% when the baseline CD4(+) T-cell count was ≥50 cells/mm(3). CONCLUSIONS: Approximately 80% of patients with a CD4(+) T-cell count ≥50 cells/mm(3) receiving maraviroc with the equivalent of at least two fully active agents achieved HIV-1 RNA<50 copies/ml at week 48 in the MOTIVATE studies. Genotypic and phenotypic weighted scores were similarly predictive of virological response.

Hepatic safety and tolerability in the maraviroc clinical development program.

Maraviroc is the first CCR5 antagonist to be approved for the treatment of HIV-1 infection. It is generally well tolerated, with a similar side-effect profile to placebo in controlled studies. Many agents used to treat HIV disease are associated with the potential for hepatotoxicity. The hepatic effects of maraviroc were analyzed across all Pfizer-sponsored maraviroc clinical trials, in which 2350 volunteers received maraviroc. Although sporadic hepatic enzyme abnormalities were reported in 34 phase 1/2a studies of up to 28-day duration, they demonstrated no dose relationship or association with hyperbilirubinemia. In the four phase 2b/3 studies in antiretroviral -naive and antiretroviral-experienced patients, there was no significant imbalance in hepatic enzyme abnormalities or hepatobiliary adverse events in maraviroc versus comparator arms up to week 96. The findings were similar in patients coinfected with hepatitis B and/or C virus, although the number of coinfected patients was small. No patient met the strict definition for Hy's Law. Two participants reported severe hepatotoxicity and although other potential causes were present, the contribution of maraviroc to these events could not be excluded. This analysis suggests that maraviroc does not present significant risks to hepatic safety when taken at the recommended doses in the populations studied.

Impact of baseline antiretroviral resistance status on efficacy outcomes among patients receiving maraviroc plus optimized background therapy in the MOTIVATE 1 and 2 trials.

PURPOSE: The MOTIVATE studies assessed maraviroc with optimized background therapy (OBT) in treatment-experienced patients with R5 HIV-1. This post hoc analysis compared outcomes between patients with and without HIV-1 resistance to epsilon3 classes of antiretrovirals at screening (triple-class-resistant [TCR] versus not-TCR [nTCR]). METHODS: Week 48 changes (N = 635) in HIV-1 RNA and CD4+ cells were compared between TCR and nTCR groups receiving twice-daily maraviroc+OBT or placebo+OBT. RESULTS: HIV-1 RNA change from baseline on maraviroc was significantly greater in the nTCR group (-2.05 vs -1.74 log(10) copies/mL; 95% CI difference 0.05-0.58 log(10)) though proportions <400 or <50 copies/mL were not. Week 48 CD4 increases were significantly greater in the nTCR group overall (mean +150 vs +110 cells/mm(3); 95% CI difference 18-62 cells/mm(3)) and in those with <50 RNA copies/mL (nTCR +192 vs +126 cells/mm(3); 95% CI difference, 19-93 cells/mm(3)) or receiving > or = 2 active OBT agents (weighted score; nTCR +184 vs +125 cells/mm3; 95% CI difference 8-110 cells/mm(3)). CONCLUSIONS: Virologic suppression on maraviroc was greater in the nTCR than the TCR group, though proportions <50 or 400 copies/mL were not significantly different. Optimal CD4 increases on maraviroc appeared to accrue from initiation before development of TCR virus.

CCR5 antagonists: host-targeted antiviral agents for the treatment of HIV infection, 4 years on.

The chemokine coreceptor 5 (CCR5) antagonists are antiretroviral agents with an extracellular, host-targeted mechanism of action against HIV. Maraviroc, the first-in-class CCR5 antagonist, received regulatory approval in 2007, becoming the first oral antiretroviral from a new class in more than 10 years. Other compounds in this class are in various stages of clinical development. In 2005, we reviewed the limited clinical data then available on CCR5 antagonists. In this follow-up review, we revisit the field and assess the clinical and virological data that have emerged in the 4 years since, with particular reference to maraviroc for which the most comprehensive data currently exist.

Maraviroc versus efavirenz, both in combination with zidovudine-lamivudine, for the treatment of antiretroviral-naive subjects with CCR5-tropic HIV-1 infection.

BACKGROUND: The MERIT (Maraviroc versus Efavirenz in Treatment-Naive Patients) study compared maraviroc and efavirenz, both with zidovudine-lamivudine, in antiretroviral-naive patients with R5 human immunodeficiency virus type 1 (HIV-1) infection. METHODS: Patients screened for R5 HIV-1 were randomized to receive efavirenz (600 mg once daily) or maraviroc (300 mg once or twice daily) with zidovudine-lamivudine. Coprimary end points were proportions of patients with a viral load <400 and <50 copies/mL at week 48; the noninferiority of maraviroc was assessed. RESULTS: The once-daily maraviroc arm was discontinued for not meeting prespecified noninferiority criteria. In the primary 48-week analysis (n = 721), maraviroc was noninferior for <400 copies/mL (70.6% for maraviroc vs 73.1% for efavirenz) but not for <50 copies/mL (65.3% vs 69.3%) at a threshold of -10%. More maraviroc patients discontinued for lack of efficacy (11.9% vs 4.2%), but fewer discontinued for adverse events (4.2% vs 13.6%). In a post hoc reanalysis excluding 107 patients (15%) with non-R5 screening virus by the current, more sensitive tropism assay, the lower bound of the 1-sided 97.5% confidence interval for the difference between treatment groups was above -10% for each end point. CONCLUSIONS: Twice-daily maraviroc was not noninferior to efavirenz at <50 copies/mL in the primary analysis. However, 15% of patients would have been ineligible for inclusion by a more sensitive screening assay. Their retrospective exclusion resulted in similar response rates in both arms Trial registration. ClinicalTrials.gov identifier: (NCT00098293) .

CCR5 pharmacology methodologies and associated applications.

The G protein-coupled chemokine (C-C motif) receptor, CCR5, was originally characterized as a protein responding functionally to a number of CC chemokines. As with chemokine receptors in general, studies indicate that CCR5 plays a role in inflammatory responses to infection, although its exact role in normal immune function is not completely defined. The vast majority of research into CCR5 has been focused on its role as an essential and predominant coreceptor for HIV-1 entry into host immune cells. Discovery of this role was prompted by the elucidation that individuals homozygous for a 32 bp deletion in the CCR5 gene do not express the receptor at the cell surface, and as a consequence, are remarkably resistant to HIV-1 infection, and apparently possess no other clear phenotype. Multiple studies followed with the ultimate aim of identifying drugs that functionally and physically blocked CCR5 to prevent HIV-1 entry, and thus provide a completely new approach to treating infection and AIDS, the world's biggest infectious disease killer. To this end, functional antagonists with potent anti-HIV-1 activity have been discovered, as best exemplified by maraviroc, the first new oral drug for the treatment of HIV-1 infection in 10 years. In this chapter, the specific methods used to characterize CCR5 primary pharmacology and apply the data generated to enable drug discovery, notably maraviroc, for the treatment of HIV infection and potentially inflammatory-based indications, are described.

A double-blind, placebo-controlled trial of maraviroc in treatment-experienced patients infected with non-R5 HIV-1.

BACKGROUND: Maraviroc, a CCR5 antagonist, is active against R5 but not X4 or dual- or mixed-tropic strains of human immunodeficiency virus type 1 (HIV-1). A phase 2b study was conducted to determine the safety and efficacy of maraviroc in combination with optimized background therapy in treatment-experienced patients infected with dual- or mixed-tropic HIV-1. METHODS: Treatment-experienced patients with an HIV-1 RNA level 5000 copies/mL who had received 3 classes of drugs and/or were infected with virus resistant to 2 drug classes and were infected with non-R5 HIV-1 were randomized to receive optimized background therapy plus maraviroc (once or twice daily) or placebo. The primary end point was change in HIV-1 RNA level from baseline to 24 weeks. RESULTS: Among 167 patients infected with dual- or mixed-tropic HIV-1, baseline mean HIV-1 RNA levels were >5 log(10) copies/mL and median CD4(+) cell counts were <50 cells/microL. From baseline to 24 weeks, patients who received placebo demonstrated a mean decrease in HIV-1 RNA levels of 0.97 log(10) copies/mL, compared with mean decreases of 0.91 and 1.20 log(10) copies/mL for those who received maraviroc once (P =.83) or twice (P +.38) daily, respectively. Mean increases in CD4(+) cell counts from baseline were 36 cells/microL for patients who received placebo, 60 cells/microL among patients who received maraviroc once daily, and 62 cells/microL among patients who received maraviroc twice daily. The incidences of serious adverse events were similar among groups. CONCLUSIONS: In this exploratory study involving extensively treatment-experienced patients with advanced, non-R5 HIV-1 infection, neither superiority nor noninferiority was statistically demonstrated for either maraviroc dosage compared with placebo at 24 weeks of treatment. TRIAL REGISTRATION: Clinicaltrials.gov identifier NCT00098748 .